javascript - D3.js - JSON data array is binding the same array element to everything - Stack Overflow

admin管理员组

文章数量:1332996

I am loading a GeoJSON data file that contains an array of objects, each object containing the vector information for a different country's outline. The same array element is being bound to every DOM element. I have e across this scope issue before in JavaScript but every change I made caused nothing to load.

I attached a jsfiddle. I use an example data file which seems to take a couple seconds to load.

My code from the jsfiddle looks like:

$(document).ready(function() {
  d3.json(
    ".geojson",
    function(error, data) {
      var myGeoJSON = data.features;

      for (i = 0; i < myGeoJSON.length; i++) {
        var path = d3.geo.path();
        var width = 960;
        var height = 600;
        var svg = d3.select("body").append("svg")
          .attr("width", width)
          .attr("height", height);

        svg.selectAll("path")
          .data(data.features)
          .enter().append("path")
          .attr("d",path)
          .attr("fill","#3e429a");
      }
    }
  );
});

I am loading a GeoJSON data file that contains an array of objects, each object containing the vector information for a different country's outline. The same array element is being bound to every DOM element. I have e across this scope issue before in JavaScript but every change I made caused nothing to load.

I attached a jsfiddle. I use an example data file which seems to take a couple seconds to load.

My code from the jsfiddle looks like:

$(document).ready(function() {
  d3.json(
    "https://raw.githubusercontent./datasets/geo-boundaries-world-110m/master/countries.geojson",
    function(error, data) {
      var myGeoJSON = data.features;

      for (i = 0; i < myGeoJSON.length; i++) {
        var path = d3.geo.path();
        var width = 960;
        var height = 600;
        var svg = d3.select("body").append("svg")
          .attr("width", width)
          .attr("height", height);

        svg.selectAll("path")
          .data(data.features)
          .enter().append("path")
          .attr("d",path)
          .attr("fill","#3e429a");
      }
    }
  );
});

• javascript
• d3.js

Share Improve this question Follow edited Oct 12, 2015 at 4:42 approxiblue 7,1221616 gold badges5252 silver badges5959 bronze badges asked Oct 2, 2015 at 8:24 Four_loFour_lo 1,1501010 silver badges2828 bronze badges 7

• You're incrementing i, but you're not using i inside your loop, or myGeoJSON for that matter. – Eterm Commented Oct 2, 2015 at 8:27
• Sorry I will edit that it breaks if I increment i, brb with the error – Four_lo Commented Oct 2, 2015 at 8:36
• d3 es back w/ cannot read length of undefined – Four_lo Commented Oct 2, 2015 at 8:44
• So, I assume you checked that the data is OK? – Cool Blue Commented Oct 2, 2015 at 9:27
• 1 Data seems fine, you can use something like .data([data.features[i]]) to load the polygons individually. Then you'd need also to center on the countries (scroll down a bit to see some countries in focus) – Pinguin Dirk Commented Oct 2, 2015 at 10:18

 |  Show 2 more ments

1 Answer 1

Sorted by: Reset to default 12 +100

You don't need to loop through the array of features. Your data file is a FeatureCollection, which D3 can draw, either as a single path element:

svg.append("path").datum(data).attr("d", d3.geo.path());

or as separate path elements, one for each feature (country):

svg.selectAll("path").data(data.features)
  .enter().append("path").attr("d", d3.geo.path())

By default D3 uses the projection d3.geo.albersUsa() which brings Hawaii to Mexico and Alaska to just outside the tropics. You can switch to the equirectangular projection to see the whole world:

d3.json(
  "https://raw.githubusercontent./datasets/geo-boundaries-world-110m/6cf0946a0f4d027d21686e8402f19b524c4f6385/countries.geojson",
  function(error, data) {
    var projection = d3.geo.equirectangular();
    var path = d3.geo.path().projection(projection);
    var width = 960;
    var height = 600;
    var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height);

    svg.selectAll("path")
      .data(data.features)
      .enter().append("path")
      .attr("d", path)
      .attr("fill", "#3e429a");
  }
);

<script src="https://cdnjs.cloudflare./ajax/libs/d3/3.4.11/d3.min.js"></script>

---

Epilogue: I initially tried to use the more mon Mercator projection, only to find that it cannot handle Antarctica. D3 draws the shape for the continent, then fills the rest of the oceans instead.

In the same D3 forum thread, the author of D3 mentioned a bug in the TopoJSON tool used to generate maps, so it might be an issue with the data file you use. If you prefer Mercator, you might need to work with the maintainer of geo-boundaries-world-110m to fix the data file, or just exclude Antarctica from your maps.

Demo of Antarctica in Mercator:

d3.json(
  "https://raw.githubusercontent./datasets/geo-boundaries-world-110m/6cf0946a0f4d027d21686e8402f19b524c4f6385/countries.geojson",
  function(error, data) {
    var projection = d3.geo.mercator();
    var path = d3.geo.path().projection(projection);
    var width = 960;
    var height = 600;
    var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height);

    var antarctica = data.features.splice(6, 1);
    // now "data" has the rest of the world
    svg.selectAll("path")
      .data(antarctica)
      .enter().append("path")
      .attr("d", path)
      .attr("stroke", "red").attr("stroke-width", 10)
      // thick borders so we can see the odd paths
      .attr("fill", "#3e429a");
  }
);

<script src="https://cdnjs.cloudflare./ajax/libs/d3/3.4.11/d3.min.js"></script>

本文标签： javascriptD3jsJSON data array is binding the same array element to everythingStack Overflow